Abstract
Paddlefish, Polyodon spathula, are large freshwater fish that once were numerous throughout the Mississippi River and Gulf Slope drainages of the United States, but they have experienced a decline in the twentieth century. After paddlefish were declared endangered in Texas in 1977, a restoration program was begun that included stocking young fish in and upstream from Livingston Reservoir, Texas. The zooplankton community of Livingston Reservoir was examined in terms of composition, abundance, distribution, and organisms appropriate as food resources for paddlefish. By comparing the range of interraker distances of paddlefish (0.06-0.08 mm) to size measurements of different zooplankton taxa, it was determined that paddlefish do not utilize small rotifers and copepod nauplii as efficiently as they do larger copepods and cladocerans. Overall zooplankton abundances were greater than those reported for other Texas reservoirs, but the community was dominated in terms of abundance and biomass by small rotifers and copepod nauplii. All taxa (rotifers, cladocerans, and copepods) were comprised of relatively small organisms. Zooplankton were distributed unevenly along the length of the reservoir, with highest abundances in the mid-portions and lower abundances near the Trinity River inflow and Livingston dam. Zooplankton were evenly distributed among the openwater and backwater stations. Cladocerans and copepods exhibited strong diel vertical migrations. A bioenergetics model was developed to predict the paddlefish biomass that could be supported in Livingston Reservoir, and predicted a density of 1. 17 kg/ha, and a range of best estimates of 0.06 to 10.45 kg/ha. The predicted densities, which might be a result of the relatively small size structure of the zooplankton community, are lower than the targets of the restoration plan, and suggest that present goals for paddlefish in Livingston Reservoir might need to be revised.
Moore, Casey Kenneth (1993). Evaluation of the zooplankton community of Livingston Reservoir, Texas, as related to paddlefish food resources. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1993 -THESIS -M8205.